Several types of dump mechanisms for pickup trucks have been proposed. Many of these dump mechanisms are difficult to install or remove from a vehicle, and require installation of accessories not only to the pickup truck bed, but also to other areas of the vehicle. Such additional accessories can include hydraulic equipment and hose connections that are attached to the engine, or hinges that are attached directly to the vehicle chassis. The cost of such hydraulic equipment can also be significant.
Some existing dump mechanisms also require a pickup truck""s tailgate to be removed before the dump mechanism can be used. For example, the dump mechanism might have a fixed pivot axis about which the dump bed rotates, with the pivot axis affixed at the rear end of the chassis at the base of the truck tailgate. Unfortunately, unloaded material may be dumped onto the tailgate unless the tailgate is removed.
Other loading and unloading systems have platforms for raising cars onto tow trucks in which the towing platform slides and pivots over the rear end of the truck chassis to form a ramp. These tow truck mechanisms typically employ hydraulic equipment to push the towing platform off the truck. Because the towing platform must touch the ground, these tow truck mechanisms are unsuitable for dumping material while moving or for lowering boats into water.
The problems identified above by the present inventor have been solved by a load transfer system that does not require hydraulic equipment, can be easily installed and/or removed in a single operation, and can be used without removing the tailgate of a pickup truck. In accordance with one embodiment, a vehicle such as a pickup truck or trailer is fitted with a cargo bed that can be moved in a rearward direction to clear an open truck tailgate before tilting the bed to unload any cargo. The unloading operation can be reversed if it is desired to load the cargo bed by sliding material up the inclined cargo bed. With this embodiment a conventional pickup truck can be converted into a dump truck. Alternatively, a vehicle can be manufactured to include an embodiment of the invention for loading or unloading the vehicle.
A mechanism for moving the cargo bed can include at least one arm having a first end coupled to the bed adjacent to a front end of the bed, and a second end of the arm coupled to the vehicle bed beneath the cargo bed. To unload cargo disposed on the cargo bed, the arm initially moves along with the cargo bed in a rearward direction along first portion of the vehicle bed, for example by sliding or rolling on wheels. After a back end of the cargo bed has cleared the vehicle bed and tailgate, the second end of the arm is caught, causing the arm to pivot about the second end, raising the front end of the cargo bed and dumping the load.
A support can be provided at the end of the vehicle or tailgate for supporting the weight of the load, and the cargo bed can pivot about the support. The support may be moveable to extend over an open tailgate when a load is being dumped, but retract to within the vehicle when the load is contained on the cargo bed. The pivot may be disposed approximately beneath the center of mass of the cargo bed and load, so that tilting the cargo bed is facilitated. The linear momentum acquired during substantially horizontal motion of the cargo bed in the initial rearward movement can be converted to angular momentum during pivoting, facilitating the lifting of the load. Stated differently, the arm acts like a pole vault stick to convert horizontal motion into a raising force. The entire load transfer process can be accomplished with simple machines such as wheels, lever arms, pulleys and inclined planes, obviating the need for hydraulic equipment. A cost-effective electrical winch can also augment the simple machines.
Other embodiments are also described below. This summary does not purport to define the invention. The claims, and not this summary, define the invention.